A succession of teething problems with the new Terminal 5 (T5) led to the sort of problems all too familiar at the west London airport.
The airport's operator, BAA, and airline British Airways, for whom the new terminal has been built after years in the planning, had hoped that the new facility would mean a fresh start for Heathrow.
But BA was forced to cancel 34 short-haul and domestic flights and had to admit that despite lots of rehearsals there had been a problem with "staff familiarisation with the terminal".
One problem seemed to follow another after the day had got off to a good start with the first flight arriving from Hong Kong eight minutes early at 4.42am.
First, staff had problems with the car park, then a computer problem led to some departing flights having to leave with no luggage aboard.
Downstairs in the giant building, passengers off the first Hong Kong flight all got their bags in quick time.
But soon it was clear there were major problems with baggage reclaim, with some passengers having to wait as long as two-and-a-half hours to collect their cases.
By lunch time the knock-on affect of all the problems lead BA to cancel 20 flights - a figure which later increased to 34.
In early afternoon, a huge, snaky queue of more than 100 people wound back from the cancellation flights desk as people lined up to try to get away on other flights or get refunds.
To add to the difficulties the luggage belt in one part of the departure lounge failed and passengers were moved further down to a workable area.
Some of those arriving early at the airport were quick to praise the magnificence of the new building which had been officially opened two weeks ago by the Queen.
But even from early morning, some passengers were moaning. They said that the road signs were not clear outside the terminal and that they were given wrong directions once inside.
British Airways said that teething problems had included "car parking provision, delays in staff security screening and staff familiarisation with the terminal".
The airline added: "We have also had some baggage performance issues."
Record production impresario Sir George Martin, famous for his work with The Beatles, was among those caught up in the difficulties. He and his wife, Lady Martin, had arrived around two hours before their flight to Zurich only to find it was over-booked.
Sir George said: "When I came here I was very excited about the new terminal, but not now."
The couple were eventually helped by a BA staff member who was able to finally get them away on their flight after all.
Some passengers were downright angry. Kate Adamson, 39, travelling from Frankfurt with her daughter Olivia, five, walked out of the baggage reclaim without her luggage after failing to reconnect with her bags after 90 minutes.
Mrs Adamson, who was visiting her parents in Maidenhead, Berkshire, said: "I am furious. Staff have been really surly. I've given up. They can send my bags on to me."
Passengers stuck in the baggage reclaim area complained that there were no announcements or that they were merely told there was a "technical problem".
Insurance broker Michael Barnfield, travelling in from Miami with his son Charles, was among those who had a two-hour wait for luggage. Visibly angry, he said: "First we spent ages on the tarmac and then we walked through a filthy corridor before getting a coach to the terminal.
"Then we had 40 minutes to get through immigration followed by an hour waiting for our bags. I know there are teething problems, but gee."
In the long queue for those who had missed or cancelled flights were retired university lecturer Walter Henry, 66, from Holloway, north London, and his wife Helen.
Mr Henry said he'd arrived in good time for a flight to Basle only to be "given six different directions from six different people to the departure lounge".
Having missed their flight the couple were hoping to get away later today.
The first flight had as its commander Captain Lynn Barton, 51, who was BA's first ever woman pilot.
Passengers on the first Hong Kong flight received special mementoes of the day as did those on the first departing flight from T5, which pushed off the stand on time at 6.20am bound for Paris.
The first passenger to arrive at the terminal - for that Paris flight - was Paul Walker, 31, a Nairobi-based Briton.
He was greeted at the terminal by BA chief executive Willie Walsh who had also seen in the Nairobi opening flight. Mr Walker said he had been "thoroughly impressed" with T5.
The first person off the initial Hong Kong flight was Clare Hammond, 44, from Greenwich, south London, who described it as a "momentous occasion" adding that BA had "really made every effort".
BA tonight stressed the 34 cancellations was out of 380 flights taking off and landing at T5 on its opening day.
The airline also felt that it was important to bear in mind that there had been a huge operation overnight moving much of BA's Heathrow operation into the new terminal.
The big disappointment for the airline, and for BAA, will be the baggage problems today, especially as both companies had trumpeted the sophisticated nature of the new baggage set-up at T5 which is capable of handling - if all goes well - 12,000 bags an hour.
BA also stressed that no amount of rehearsals and dummy runs can really replicate a working day with real passengers, real planes and real luggage.
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